This adds support for tombstoned files to clay. It does not include any
way to actually tombstone them; that is left for later.
This allows tombstoning at the level of a file. Precisely, this expands
+blob:clay by adding a %dead case:
+$ blob :: fs blob
$% [%delta p=lobe q=[p=mark q=lobe] r=page] :: delta on q
[%direct p=lobe q=page] :: immediate
[%dead p=lobe ~] :: tombstone
== ::
Thus, we maintain the invariant that every lobe corresponds to a blob,
but now a blob may be an explicit tombstone.
Details:
- This has not been tested at all, except that it compiles and boots.
- This does not have a state adapter from master. The only state change
is the definition of +cach.
- Additionally, out-of-date ships may unexpectedly receive a %dead blob
from a foreign clay which would interfere with their ability to download
that desk. No code changes necessary, but sponsors should avoid
tombstoning files in %base for a while so their children can get the
update.
- A merge will only fail if the tombstoned file conflicts with another
change. Note that as written, merging from a past desk *can* bring a
tombstoned file to the head of a desk. Possibly this shouldn't be
allowed.
This also includes a couple refactors that were made possible by ford
fusion (since everything is synchronous now) but never got done. In
both cases we get to remove a monad, which simplifies the code
considerably.
- refactor +merge's error handling to use !!/mule instead of threading
through errors
- refactor all +read-* functions and related parts of +try-fill-sub to
eagerly convert lobes to cages.
We also add support reading %a/b/c/e/f/r/x from past and foreign desks,
when possible. Apologies that all of these are in one commit, it was
all a single chunk of work.
This is a draft until we have a way to tombstone. I suspect we'll want
to have a mechanism of keeping track of gc roots and trace to remove,
but this PR doesn't suggest any particular strategy.
We do not care about what's on foreign, the local desk is the thing
we're taking action on. This is more robust in the face of absent
information about foreign desks etc.
Also stops pretending to take-commet during take-merge-main. We'll get a
separate commit event.
If a remote commit is downloaded that simultaneously removes an agent from
desk.bill but also removes the associated source files, then the commit
will fail as gall will not have received the card to kill the agent yet.
Instead, we read our foreign copy of the bill in +take-download, and
kill any necessary agents there, preventing a reload of the deleted
agent from occurring.
When we receive the %mere gift from clay, the kernel has not yet been
reloaded. This means any attempts to bump desks will fail, as they will
be bumped against the old kernel. Rectifies this by continuing the %base
desk update flow in +on-load, instead of +take-merge-main. Also adds a
wef=(unit weft) to the state in order to discriminate whether or not the
kernel has just been reloaded
